Inductive coupling device



1,641,925 Sept. 6,1927. J. G GABRIEL 1 INDUCTIVE COUPLING DEVICEOriginal Filed -29, 1923 {J [6 4 J 4 RECEIVER T L6 9 9o" we AngularRofafion [5 to secure this result by providin Patented Sept. 6, 1927.

UNITED STATES PATENT OFFICE.

JOHN C. GABRIEL, OF NEW YORK, N. Y., ASSIGNOR TO WESTERN ELECTRICCOMPANY, INCORPORATED, 015 NEW YORK, N. Y., A CORPORATION OF NEW YORK.

/ INDUCTIVE COUPLING DEVICE.

December 29, 1925. Serial No. 78,149.

Original application filed December 29, 1928, Serial No. 688,299.Divided and this application filed This invention relates to a couplingdevice and more particularly to an arrangement whereby the couplingbetween two circuits may be varied.

I This application is a division of the application Serial No. 683,299for high frequency transmission, filed December 29, 1923,

' to J. C. Gabriel.

In connection with certain apparatus, for

W example, that used in radio systems, it is desirable to be able toaccurately adjust the degree of coupling between associated circuits.

- In general it has heretofore been pro osed a justable coupling devicesor vario coup ers comprising solenoidal coils, one of whlch 1s rotatablerelatively to the other.

In this type of vario coupler the ad ustment for the entire range ofcoupling variation is aiiected by a 90 rotation of the rotatable coil.For equal angular ad ustments of the coil the rate of change of couplingis non-uniform throughout the range of adjustment and increases sharplynear the positions of minimum and maxlmum couplin This rapid andirregular variation of the coupling constitutes a marked disadvantage, I9 since it increases the difliculty of efiectlng an accurate adjustmentof the coupling, es-

pecially at or near the minimum limit.

An object of this invention Is to permit the couplin between electricalclrcuits to be 5 varied uni ormly from maximum to minipling devicethroughout the range of operation.

A feature of the inventlon relates to the provision of a vario couplinghaving windings such that the variation of coupling is substantially alinear function of the angle of rotation of the movable element over 180de ees.

The novel features and combmations which are believed to becharacteristlc of this invention will be defined in the subjoinedclaims.

The invention both as to its constructlon and operation may beunderstood by reading the following descri tion in connection with theaccompanying rawings, in which Fig. 1 shows the construction of acoupling unit or vario coupler in accordance with this invention; Fig. 2shows diagrammatically a circuit including the coupler; and Fig. 3illustrates curves which serve to explain the operation of thisinvention.

In Fig. 1 there is shown a variable inductance or vario couplercomprising two coils, 1 and 2. Each of these coils comprises acylindrical supporting form having a slotted portion at one end uponwhich the conducting wire is wound to constitute a solenoidal windingand a figure 8 winding. By figure 8 type is meant the general typeillustrated in the U. S. patent to Ourtis 1,367,734, February 8, 1921.

Coils 1 and 2 are 'so arranged that the slotted portions of thesupporting forms, upon which the figure 8 turns are wound, face oneanother and are directly opposed. As herein shown coil 1 isstationary'while coil 2 is mounted on the shaft 7 carrying the knob ordial 12 by which it may be rotated. The movable coil is connected to anexternal circuit or apparatus by leads 8 and 9 brought out through theshaft 7. If desired these leads may be connected to flexible conductors10 and 11.

In Fig. 2 a coupler, such as has been described above, is shown includedin a radio receiving system. The stationary coil is included in theantenna circuit and the movable coil is included in the tuned receivingcircuit associated with the antenna.

Fig. 3 is a graphic representation of the coupling variation obtainablewith a vario coupler having solenoid windings and that which may beobtained by using the vario coupler described above. The couplingcharacteristic of vario couplers having solenoid coils is represented bycurve B, while the characteristic of the coupler hereinbefore describedis represented by the curve A.

grees. Moreover, as shown in curve 38, the rate of change of coupling isvariable at all points throughout the range of adjustment of the movablecoii and this variation is especially marked at or near the maximum orminimum values. in accordance curve A, the rate of change of cor uniformbetween maximum and .1 values.

As stated above, each coii comprises both solenoidal and figure iiwindings. The numher of turns in the solenoid-e1 winding for each coilin relation to the number of turns oi the figure 8 winding isproportioned in such a manner that the mutual inductance of the twosolenoidal windings is substantially equal to that of the two figurewindings. When the coils consist of a few turns the number of each typewill be approximately equal, the exact proportion being determinedexperimentally.

As coil 2 is rotated the mutual inductance between the solenoidalwindings of the two coils will remain constant. The mutual inductancebetween the figure 8 windings, however, will be continuously variableand, beyond a certain point, the electromotive force thereby induced incoil 2 will oppose that induced by the cooperation of the solenoidalwindings. When the coils are in such a position that the figure 8windings of each coil are directly opposed, the direction of the E. M.F. induced in the figure 8 windings of coil 2 will be the same as thedirection of the E. M. F. induced therein by the solenoidal windings ofcoil 1. Maximum coupling will occur in this position, since the E. M. F.induced in the figure 8 windings is added to the E. M. F. produced bythe solenoidal winding. With the rotation of coil 2 the value of thecurrent in the figure 8 winding decreases, until it reaches zero whenthe angle of rotation is 90. As coil 2 is rotated further, that half ofthe figure 8 winding which was initially opposed to the upper half ofthe figure 8 winding of coil 1 is now approaching the lower half of thefigure 8 winding of coil 1. Since, due to the figure 8 construction ofthe windings, the direction of flow of current in the lower half of coil1 is opposite to the direction of flow in the upper half, the E. M. F.induced in the figure 8 winding of coil 2 will be changed in directionand will consequently oppose the E. M. F. induced in the solenoidalwinding of coil 2. As the angle of rotation of coil 2 is increased from90 to 180, the opposing E. M. F. induced in the figure 8 windingincreases until minimum coupling is reached, at which time the E. M. F.induced in the solenoidal winding is entirely offset by the E. M. F.induced in the figure 8 winding. In other words, at maximum couplin theeffect of the mutual inductance of the gure 8 windings is equal andadded menace to the mutual inductance of the solenoidal windings, whileat minimum couplin the efi'ect of the mutual inductance of the figure t3windings is equal and opposed to the mutual inductance of the solenoidalwindings.

Eetween and minimum the coupling value varies by an amount whichproportional to the de ree of angular rotation of the coil 2, there hygiving a chan e of coupling value which is linear over the entireadjustment range.

in view of the preceding description it will be seen that this inventionprovides an arrangement in which rotation of the movable element throughan angle of 180 is necessary to vary the coupling over the completerange, and in which the rate of change of coupling is the same for equalangular adjustments of the movable element at. all points in itsoperation, whereby very fine coupling adjustments may be readily andaccurately made. While applicant for the purpose of disclosing theinvention has described a coupler comprisin two coils, modificationssuch as the use 0 additional coils will readily suggest themselves,audit is to be understood that this invention is limited only by theattached claims.

What is claimed is:

1. A coupling arrangement com rising coaxially arranged stationary anmovable coils havin windings composed of a solenoid section an a figure8 shaped section, and means for rotating said movable coil through 180to produce a coupling variable in the same sense and substantiallylinearly from maximum to minimum.

2. A variable inductivedevice, comprising coils having windings composedof a solenoid section and a figure 8 shaped section.

3. A coupling device comprising a. plurality of coils electromanetically related, each coil being compose of a solenoidal winding and afigure 8 winding, and means for rotating one of said coils.

4. A coupling device comprising two coils coaxially mounted androtatable relatively to one another, each of said coils including asolenoid winding and a figure 8 winding.

5. A coupling device including electromagnetically related coils, meansfor relatively rotating said coils, each of said coils comprising acylindrical supporting form having an unslotted portion and a slottedportion, and a winding consisting of solenoidal turns and figure 8 turnswound respectively uponsaid unslotted portion and said slotted ortion.

6. A coup ing arrangement comprising a plurality of coilselectromagnetically related, each of said coils comprising a.substantially cylindrical form, a portion of which is slotted to permitfigure 8 turns to be wound upon it, a. winding consisting of. solenoidalturns in series with said figure 8 turns wound upon said form, and meansfor rotating one of said coils through 180 to vary the coupling fromminimum to maximum.

7. A coupling arrangement consisting of two inductively related coilseach of which is composed partly of solenoidal windings and pzrtly offigure 8 windings, said windings ing arranged to establish a constantmutual inductance between the coils, the rotation-of one of said coilscontrolling the electromotive force induced in the secondary coil byinducing a second elecihomotive force which over one part of the rangeof adjustment of the rotary coil tends to increase, and over anotherpart of the range of adjustment of the rotary coil tends to decreasesaid first mentioned electromotive force at a substantially uniformrate, whereby there is produced a coupling variation which isadjustment.

8. In a variable coupling arrangement, means for varying the couplingbetween two circuits with a greater degree of uniformity than can beobtained by varying the relative position between two solenoids,comprising coupling coils each made up of a combination of a solenoidsection and a figure 8 section of coil.

9. In a radio system, means for tuning the receiver for incoming wavescomprising a coupling coil made up of a combination of a solenoidsection and a figure 8 shaped section.

In witness whereof, I hereunto subscribe my name this 28th day ofDecember A. D., 1925.

JOHN C. GABRIEL.

substantially linear over the entire range of i

